Electric and hybrid vehicles have recently become a more common sight on roads worldwide. They have one thing in common and that is they all require a large and powerful rechargeable energy storage, for example a rechargable battery. Such rechargable batteries have a limited runtime every time it is recharged and a user typically has a way of monitoring an estimated currently available power and energy of the battery.
The available power, or other operation conditions of the battery such as for example state of charge (SoC) is typically estimated using a model. The model may need inputs relating to the battery, for example capacity and resistance of the battery cells of the battery, or the temperature of the battery. A commonly type of model comprises an equivalent circuit model through which a current-voltage characteristics is obtained for the model battery.
One example of a method for estimating a state of health of a battery is disclosed by U.S. Pat. No. 7,373,264 in which an equivalent circuit model and a recursive formula is used. The parameters of the model are updated as one part of the model.
The complexity of estimating e.g. state of charge increases when taking into account both battery parameters and aging of the battery. It would be desirable to somehow in an efficient way include these in the model in order to increase the accuracy of the estimated e.g. state of charge.